﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;

namespace Web
{
    public partial class png : System.Web.UI.Page
    {

        private string CreateRandomCode(int codeCount)  
        {  
            string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";  
            string[] allCharArray = allChar.Split(',');  
            string randomCode = "";  
            int temp = -1;  
            Random rand = new Random();  
            for (int i = 0; i < codeCount; i++)  
            {  
                if (temp != -1)  
                {  
                    rand = new Random(i * temp * ((int)DateTime.Now.Ticks));  
                }  
                int t = rand.Next(61);  
                if (temp == t)  
                {  
                    return CreateRandomCode(codeCount);  
                }  
                temp = t;  
                randomCode += allCharArray[t];  
            }  
            return randomCode;  
        }  

         private void CreateImage(string checkCode)  
        {  
            int iwidth = (int)(checkCode.Length * 20);  
            System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 25);  
            Graphics g = Graphics.FromImage(image);  
            Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);  
            Brush b = new System.Drawing.SolidBrush(Color.White);         
            g.Clear(Color.Black);  
            g.DrawString(checkCode, f, b, 3, 3);  
            Pen blackPen = new Pen(Color.Black, 0);  
            Random rand = new Random();                 
            System.IO.MemoryStream ms = new System.IO.MemoryStream();  
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);  
            Response.ClearContent();  
            Response.ContentType = "image/Jpeg";  
            Response.BinaryWrite(ms.ToArray());  
            g.Dispose();  
            image.Dispose();  
        }  

        protected void Page_Load(object sender, EventArgs e)
        {        
                    string gif = CreateRandomCode(4);
                    Session["gif"] = gif;
                    CreateImage(gif);
        }

       
    }
}